lex_float_test.nx

lex_float_test.nx -- self-test for TK_FLOAT lexing. Verifies: (1) "3.14" -> TK_FLOAT, int_val=3, text0=14, text1=2 (2) "0.5" -> TK_FLOAT, int_val=0, text0=5, text1=1 (3) "42" -> TK_INT , int_val=42 (integer unchanged) (4) "1.0f" -> TK_FLOAT, int_val=1, text0=0, text1=1 (suffix consumed) (5) "2.718e0" -> TK_FLOAT on the "2.718" portion. Exponent tokenisation isn't wired yet; the 'e0' tail falls through to the identifier lexer. This test confirms the float portion is correctly isolated. Once parse.nx consumes TK_FLOAT + emits VK_CONST_FLOAT into the IR, end-to-end f32 codegen (the final piece after regalloc dfe10f8) is runnable.